1. Field of the Invention
The present invention relates to a face importance level determining apparatus and method for determining an importance level for a photographer with respect to a face of a person appearing in an image, and an image pickup apparatus having a face importance level determining function.
2. Description of the Related Art
An increasing number of image pickup apparatuses using solid-state image pickup devices, such as digital still cameras and digital video cameras, having a function called a “scene mode” that provides optimum control, such as automatic exposure control, according to various scenes during the capture process have been available. For example, a “portrait mode,” which is suitably used for photography of the human face, is a mode whose exposure control target is set higher than general modes to thereby allow a human face image to be captured with optimum brightness. Therefore, images captured with beautiful skin tones can be obtained.
Recently, techniques for detecting a face from a captured image and automatically focusing on the detected face or automatically correcting the image quality depending on the face have been developed.
One known technique for detecting a face from a captured image signal is to use an average face image as a template to perform matching with an input image signal (see, for example, Japanese Unexamined Patent Application Publication No. 2003-271933 (paragraph numbers [0051] to [0053] and FIG. 6)). If a face appearing in a captured image is tilted at an angle, it is difficult to correctly detect such a face. Therefore, there have been proposed techniques, such as determining the angle of the face and rotating the face image according to the determined angle before performing the matching. In one known technique, a center line of the face is detected, the degree of similarity to the center line is determined on the basis of the face symmetry, and the angle of the center line with a high degree of similarity is output as the angle of the face (see, for example, Japanese Unexamined Patent Application Publication No. 9-171560 (paragraph numbers [0032] to [0044] and FIG. 4)).